With the evolution of wireless communication systems, there is an increasing demand for larger coverage, higher capacity and higher data transmission rate. Currently, a solution to satisfy this demand is to deploy pico cells. However, in many cases it is a difficult to establish a backhaul link between a pico Base Station (BS) and its associated core network (CN) by paving an optical fiber or providing a Line of Sight (LOS) radio link between them. Moreover, since there are different wireless communication systems with different radio access technologies co-existing in the market, such as Global System for Mobile Communication (GSM), Wideband Code Division Multiple Access (WCDMA) and Long Term Evolution (LTE), it is very expensive to establish dedicated backhaul links for each of these systems.
Therefore, an LTE-based non-LOS wireless backhaul solution has attracted more and more attention from telecommunication operators. According to this solution, a backhaul User Equipment (UE) and a backhaul evolved NodeB (eNB) are introduced for establishing a wireless backhaul link. As shown in FIG. 1, a backhaul UE is an LTE terminal connected with a pico BS via a wired connection (e.g., Ethernet connection) and acts as a wireless router for receiving backhaul packets (e.g., Internet Protocol (IP) packets) from the pico BS and forwarding them to a backhaul eNB via a radio link. The backhaul eNB then forwards the backhaul packets to a core network node. A backhaul eNB may also act as an ordinary eNB serving ordinary UEs in its cell.
However, there is a problem with the above wireless backhaul solution. As shown in FIG. 1, in the prior art, upon receiving a backhaul IP packet from the backhaul UE, the backhaul eNB simply encapsulates the IP packet into a General Packet Radio Service (GPRS) Tunnel Protocol (GTP) packet and sends it to an LTE Gateway (GW), which can be a Serving GW (S-GW) or Packet Data Network (PDN) GW (PDN-GW) in an LTE core network, across an LTE transport network.
The GW then decapsulates the GTP packet to obtain the IP packet and sends the IP packet to its destination. However, usually the IP packet from the pico BS is destined to a core network node that is not located in the LTE core network, e.g., a GSM core network node. In this case, the routing of the backhaul packet is inefficient since it unnecessarily travels through the entire LTE transport network even if its destination node is geographically or topologically close to the backhaul eNB. This causes unnecessary burden on the LTE transport and core networks. The dashed lines with arrows in FIG. 1 illustrate the path the packet needs to travel through before it finally reaches its destination.
The 3rd Generation Partner Project (3GPP) TS 23.401 v12.2.0 discloses a technique known as Selected IP Traffic Offloading (SIPTO). According to this technique, based on Access Point Name (APN) or UE identifier (ID) information transmitted from a UE, a Mobility Management Entity (MME) in the LTE core network selects a GW (S-GW or PDN-GW) that is physically close to an eNB serving the UE. The MME notifies the eNB of the selected GW and then the eNB can send packets originated from the UE to the selected GW which is close to it.
However, the SIPTO technique is based on a Domain Name System (DNS) mechanism in the MME, which is complicated. The traditional DNS mechanism needs to be enhanced with topological and/or geographical information such that the MME can determine which GW is close to the eNB according to Full Qualified Domain Name (FQDN). Moreover, it is not trivial to maintain such topological and/or geographical information in the DNS mechanism due to dynamics of the UE and the large number of UEs and eNBs in the network.
Therefore, there is a need for an improved solution for routing backhaul packets efficiently.